Prior art golf clubs have generally been made either with gradually tapered shafts or with shafts having a plurality of gradual steps along the length thereof. When golf clubs with such shafts are swung, the shaft bends during an initial portion of the players downswing to store energy therein. During a final portion of the downswing, such energy is released to accelerate the club head and, ideally, produce maximum velocity of the club head at impact. It is difficult to feel the action of the shaft and club head and obtaining the optimum action requires that the player develop a uniform swing action through long practice and that the character of the shaft in relation to the mass of the club head be properly matched to the characteristics of the player's swing action. Variations have been made in the materials used in shafts without changing the basic mode of operation thereof. Changes in the configuration of shafts have also been proposed. For example, in 1926, the Pollack British Pat. No. 256,049 proposed pressing the metal of a shaft inwardly at diametrically opposed paints to enable the shaft to yield, such being done at a plurality of points on the length of the shaft or in a manner such as to form one or more portions of the shaft into a shape of oblong cross-sectional form. In the 1936 Barnhart U.S. Pat. No. 2,050,554, a shaft was proposed having an upper portion tapered downwardly to a medial region at which the shaft wall was bulged outwardly to form a stiffening shoulder, with a lower portion of the shaft being tapered downwardly from the shoulder to the tip end secured to the club head. It is not known whether such shafts were ever actually used to any substantial degree and in any event, it is not believed that they ever enjoyed any substantial degree of acceptance. The action of such shaft in regard to "feel" and release of stored energy is difficult to analyze, especially as to complex configurations such as disclosed in the Pollack patent, but it is believed that the overall action of the shafts would be similar to that obtained with conventional shafts.
In my application for a design patent, Ser. No. 575,803, filed May 8, 1975, I disclose a shaft having a single step at the junction between an upper larger diameter portion and the lower smaller diameter portion, the length of the smaller diameter portion being on the order of one-quarter or less of the total shaft length. Since about late 1974 or early 1975, that shaft has been used commercially and publicly but only in putters, although I had previously experimented with use of similar shafts in woods and irons. In putters, strength and considerations with regard to obtaining maximum head velocity at impact are not important and the ornamental appearance of the shaft is of primary importance. Psychological factors are important in all aspects of golf, but are especially important in putting. So far as I know, shafts with any step similar to that provided in the aforesaid putters have not been used for wood or iron clubs other than in the course of my own experimental work and research.